1. Field of the Invention
This invention relates to an electrophotographic process for producing color images and an electrophotographic photosensitive member.
2. Description of the Prior Art
According to conventional methods for forming colored images by means of an electrophotographic photosensitive member, original colored images are exposed at least three times and the exposure is effected through a color filter which is usually a red, green or blue filter. After each exposure, the latent images are developed with a toner whose color is a complementary color to the color of the filter to produce toner image according to an electrophotographic process.
For example, a photosensitive member is charged, imagewise exposed through a red filter, developed with a cyan toner and the image thus developed is transferred to a receiving paper and then the same procedure is repeated by using a green filter and a blue filter followed by developing with a magenta toner and a yellow toner, respectively, to produce colored images. When a black toner is used for an additional image
forming step for improving image quality of colored images, a somewhat more intensive exposure is effected without using a color filter and a black toner is attached electrostatically to the surface of the photosensitive member corresponding to black portions of the original images.
As mentioned above, conventional colored image formation by electrophotographic means needs at least three exposures with different filters and the procedures are complicated. Further, in conventional methods, between the three exposures and developments there are effected corona chargings, but in case of corona charging, it is, in general, very difficult to control the electric charge amount. Therefore, control of the tone of color images is effected by adjusting the exposure amount. Such a way of controlling the tone can not be easily effected at a high accuracy, and further, it is more difficult to control each color tone separately.